Manufacturers, owners and operators of trucks, such as single and tandem tractor trailor combinations, must be cognizant of loads placed on the trucks for a number of reasons. First, these entities must be assured of safe operation of the vehicle. The weight capacity of a truck is often known by the operator thereof by reason of the manufacturer of the truck placing on the vehicle a warning notice of such weight capacity. Exceeding the weight capacity can place the truck under unnecessary strain, which could result in accidents or breakdown of the vehicle during operation of the same. In addition, overloading the truck can impair the life of the vehicle and increase repair costs, tire expenses, etc. Also, from the manufacturer standpoint, its and its product's reputation is affected by reason of complaints from owners or purchasers of the vehicles of such repair costs, vehicle breakdown, etc. Further, operators must be aware of vehicle load condition so as to avoid violating road weight safety regulations imposed by state and federal governmental bodies.
The cautious owner/operator of the vehicle, being aware of the foregoing negative consequences of vehicle overload, often, in order to be on the safe side, "underloads" the truck thereby reducing the operative efficiency thereof by increasing the unit cost per pound of the cargo loaded.
Therefore, it has been found advantageous to provide a device adapted to mount to a vehicle and advise the vehicle operator of the overload or underload condition of the vehicle so that the weight capacity of the same will not be exceeded, governmental regulations will not be violated and the operating efficiency of the vehicle will not be reduced because of failure to load the truck to its "rated" capacity.
When a load is placed on a vehicle, the frame thereof depresses relative to the vehicle axle which remains stationary relative to the clearance above ground. The vertical distance between the vehicle frame and axle will thus change or decrease as heavier loads are placed on the vehicle. It has thus been found favorable to provide a device which functions between these moving and stationary parts of the vehicle to detect the change in distance between such parts and to convert such change in distance into a measurable property which can be translated to the vehicle operator to indicate vehicle load weight.
Many such devices are known. For example, U.S. Pat. Nos. to Askew, 3,867,990 and 3,955,636, issued Feb. 25, 1975 and May 11, 1976, respectively, disclose a device for measuring and providing an indication of loads exerted on a vehicle and comprising a mounting bar secured to the vehicle frame, a collar adjustably mounted to the bar, a transducer mounted to the collar, a toggle arm pivotally mounted to the transducer, and a sensor arm pivotally mounted at the upper end thereof to the toggle arm and at the lower end thereof to the vehicle differential. In this manner, when a load is exerted on the vehicle frame, the same depresses relative to the differential which urges the toggle arm to rotate. The transducer converts the angular deflection of the toggle arm into a potential electric property. An electrical gauge positioned, for example, in the vehicle cockpit, is adapted to receive the output from the transducer to inform the vehicle operator of the load condition of the vehicle.
The transducer includes a spindle associated with a light beam, a shutter for the light beam and a photoelectric cell receiving the light beam. Alteration of the distance between the frame and the differential detected by the toggle arm is followed by proportional rotation of the spindle which causes the light beam to be proportionally modified by the shutter in a manner which is detected by the photoelectric cell and converted into a dielectric property output received by the electrical gauge.
In addition, U.S. Pat. No. to Goodale, 1,956,096, issued April 24, 1934, discloses a device for detecting vehicle load weights and comprising a sensor secured to the vehicle frame and an actuating lever pivotally mounted at one end to the sensor and at the other end to an actuating bar securely connected to the vehicle axle. The sensor comprises a piston connected to the lever arm through a rack and pinion assembly. In operation, when a load is exerted on the vehicle frame, the actuating lever rotates and causes the piston, through fluid pressure, to move a pointer of a gauge to a position indicating the load exerted on the vehicle.